Advancements in satellites, and the enhancements to telecommunications and other services that sophisticated satellites make possible, have dramatically increased the number of commercial satellites being launched. As each launch is an expensive event, there has been a trend toward increasing the number of features and components on satellites, allowing multiple users to share the costs and benefits of the satellite launch. Increased features have resulted in an increase in the size of these satellites, and consequently the size of the launch vehicles required to carry these satellites into their operational orbit. Generally, satellite launch vehicles are multi-stage rockets, with each stage including its own fuel tank, with domes. It is in the manufacture of these larger rocket domes that current manufacturing methods fall short.
Rocket domes have typically been fabricated from single blanks of aluminum alloys or other alloys that are hot spun over mandrels to form the desired shape. Common mandrel spinforming methods include clamping a blank between a rotatable spindle and a die, or mandrel, corresponding to the shape to be formed. The clamped assembly is then rotated and the blank is heated while a tool, such as a spinning roller, is used to apply pressure, progressively, to a small area of the metal blank, thereby causing the small area to deform in the direction of the pressure. As the metal blank rotates, a circumferential band of the blank is progressively deformed and, by moving the spinning roller in a radial direction with respect to the rotating metal blank, the desired shape is produced.
Other spinning methods, such as those described in U.S. Pat. Nos. 5,235,837 and 5,426,964, utilize a numerically controlled second roller in place of the mandrel to exert directed forces on both sides the blank to deform the material in the desired manner. These methods are useful for cold rolling exotic materials, or for hot rolling tanks or other pressure vessels. However, dual roller systems have not traditionally been used in the production of rocket domes of the characteristics described herein. The use of this type of equipment for very large domes will necessitate welding a flange to the polar and equatorial region of the dome. Also, if dome configuration had nozzles with the dome shell, this would also have to be welded into place.
Traditionally, rocket domes have been manufactured by the mandrel spinning process from blanks having a surface area that is greater than or equal to the surface area of the domes to be spun. This process results in a dome having the desired diameter and a substantially constant material thickness. Traditional hot mandrel spinning methods have been effective, as long as the surface area of the necessary blank was smaller than the largest commercially available blank diameter. However, to manufacture domes for large rockets using traditional mandrel spinning techniques would require a circular blank with an outside diameter well in excess of the maximum commercially available blank size.
One possible solution to this problem is to weld several blanks together to provide a starting outside diameter of sufficient size. However, this is a very expensive approach due to the meticulous processes that must be employed to insure the integrity of the welds, and the subsequent x-raying and testing required to qualify each weld.
Another solution would involve the production of a rolling press that could produce plates of the desired thickness having diameters in excess those that are currently commercially available. However, neither material fabricators nor spinning manufacturers are likely to invest in such a press as the low demand for plates of these widths, and the high cost of designing and building this equipment, make this solution an unprofitable one.
A method of manufacturing a rocket dome from an undersized blank that does not require multiple blanks to be welded together, does not require blanks to be rolled to the desired diameter, and may be performed on common hot mandrel spinning equipment is not known in the art.